Isolated protoplasmic droplets of the alga Nifella were investigated with microelectrodes under current clamp conditions. The following observations were made:
Long pulses of either polarity yielded almost symmetric current-voltage relations. Near the rather small resting potential (inside negative) the measuring points lay on a straight line corresponding to an apparent surface membrane resistance of 1.7±0.45 kΩ (mean ± S.E.M.,n=5).
Experiments with various pulse programs revealed no mechanism comparable to Na inactivation but stressed the electrical symmetry of the droplet with respect to the resting potential.
Changes of the [Ca2+] in the bathing medium between 0 and 10 mM as well as of the pH between 5 and 9 did not influence the responses. Replacing K+ by Na+ (or vice versa) or exchanging NO 3 − for acetylglycine or Cl− was also ineffective.
These observations are not consistent with a normal excitable surface membrane. Similar responses are obtained with a RC network which is described and which may have its substrate in histological peculiarities of the protoplasmic droplet.
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Hodgkin, A. L., Huxley, A. F.: A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. (Lond.)117, 500–544 (1952)
Inoue, I., Ishima, Y., Horie, H., Takenaka, T.: 124. Properties of excitable membrane produced on the surface of protoplasmic drop in Nitella. Proc. Japan Acad.47, 549–553 (1971)
Inoue, I., Ishida, N., Kobatake, Y.: Studies of excitable membrane formed on the surface of protoplasmic drops isolated from Nitella. IV. Excitability of the drop membrane in various compositions of the external salt solution. Biochim. biophys. Acta (Amst.)330, 27–38 (1973b)
Inoue, I., Ishida, N., Kobatake, Y.: Studies of excitable membrane formed on the surface of protoplasmic droplets isolated from Nitella. V. Effect of the chemical modification of membrane proteins with SH reagents on excitability. Biochim. biophys. Acta (Amst.)367, 24–31 (1974)
Inoue, I., Ueda, T., Kobatake, Y.: Structure of excitable membranes formed on the surface of protoplasmic drops isolated from Nitella. I. Conformation of surface membrane determined from the refractive index and from enzyme actions. Biochim. biophys. Acta (Amst.)298, 653–663 (1973a)
Iwasaki, N., Kishimoto, U.: Electrical characteristics of the protoplasmic droplet isolated from Nitella internodes. Proceedings of the 33rd Annual Meeting of the Botanical Society of Japan, p. 81, 1968
Kamiya, N., Kuroda, K.: 39. Cell operation in Nitella. I. Cell amputation and effusion of the endoplasm. Proc. Japan Acad.33, 149–152 (1957)
Kishimoto, U.: Voltage clamp and internal perfusion studies on Nitella internodes. J. cell comp. Physiol.66, Suppl. 2, 43–54 (1967)
Koppenhöfer, E.: Electrical excitability of protoplasmic droplets from Nitella cells. Pflügers Arch.347, R 36 (1974)
Koppenhöfer, E.: Electrical responses of protoplasmic droplets from Nitella. Pflügers Arch.355, R 82 (1975a)
Koppenhöfer, E.: Electrical responses of isolated protoplasm from Nitella. Pflügers Arch.358, 179–187 (1975b)
Koppenhöfer, E., Schramm, M.: Intracellular application of strong currents under current clamp conditions. Pflügers Arch.350, 335–340 (1974a)
Koppenhöfer, E., Schramm, M.: A method for electrical measurements on isolated protoplasmic droplets from Nitella. Pflügers Arch.350, 341–346 (1974b)
Miyake, M., Inoue, I., Kobatake, Y.: Studies of excitable membrane formed on the surface of protoplasmic drops isolated from Nitella. III. Impedance of the surface membrane. Biochim. biophys. Acta (Amst.)323, 367–377 (1973)
Smith, M. E., Smith, L. B.: Piperazine dihydrochloride and glycylglycine as non-toxic buffers in distilled water and sea water. Biol. Bull.96, 233–237 (1949)
Takenaka, T., Inoue, I., Ishima, Y., Horie, H.: 125. Excitability of surface membrane of protoplasmic drop produced from protoplasm in Nitella. Proc. Japan Acad.47, 554–557 (1971a)
Takenaka, T., Inoue, I., Ishima, Y., Horie, H.: Excitability of semiartificial membrane produced from endoplasm. Proc. IUPS IX, 555 (1971b)
Ueda, T., Inoue, I., Kobatake, Y.: Studies of excitable membrane formed on the surface of protoplasmic drops isolated from Nitella. II. Tension at the surface of protoplasmic drops. Biochim. biophys. Acta (Amst.)318, 326–334 (1973)
Ueda, T., Muratsugu, M., Kobatake, Y.: Roles of Ca2+, phospholipids and proteins in the excitable membrane of protoplasmic droplet isolated from Nitella. Biochim. biophys. Acta (Amst.)373, 286–294 (1974)
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Koppenhöfer, E. Electrical responses of isolated nitella protoplasm — Excitations or artifacts?. Pflugers Arch. 361, 263–267 (1976). https://doi.org/10.1007/BF00587291
- Isolated protoplasm
- Electrical responses
- RC network